In recent years, there is a demand for development of toners having excellent fusing ability and storage stability, etc., from the viewpoint of achieving higher image qualities.
As toners having not only a good low-temperature fusing ability but also a good charging property, there is disclosed a toner using a resin binder which contains a crystalline polyester whose surface is coated with an amorphous polymer (JP 2004-191927A). Also, there are disclosed a toner which is improved in fusing ability by an emulsification and aggregation method including a step of causing fusion between fine particles (JP 2007-248666A), and a toner which is improved in fusing ability or long-term storage property by using, as a resin binder, fine particles prepared by dispersing a polyester in water for dissolution and reduction in viscosity (JP 2005-128176A).
In addition, in order to provide good images which are kept stable even when used for a long period of time, there is disclosed a process for producing a toner for development of electrostatic latent images which process includes an aggregating step of mixing a dispersion in which non-crystalline polyester resin particles are dispersed and a dispersion in which crystalline polyester resin particles are dispersed, with each other to form aggregated particles; and a fusing/coalescing step of heating the resulting aggregated particles at a temperature not lower than a glass transition temperature of the non-crystalline polyester resin to obtain fused and unified particles thereof, wherein a mixture of the non-crystalline polyester resin and the crystalline polyester resin has a specific weight-average molecular weight (Mw) and a specific ratio of the weight-average molecular weight (Mw) to a number-average molecular weight (Mn) (Mw/Mn) (JP 2008-158197A).